Re: Is there a rigorous definition for 'primary partition' ?

The MBR disk structure contains several sectors which are partition tables.

Each of these sectors has 4 entries, and each entry can be:
- empty
- describe the partition
- describe the link to the next PT sector (yes, PT is linked list). This
next PT sector is usually called "extended partition table". There can be only
one such forward link in a PT sector.

The first PT sector is MBR itself - sector 0 of the physical disk.

MS-DOS (including Win98/Me based on MS-DOS) requires that the first PT
sector has only 1 valid partition entry (and possibly the link to the next PT
sector too). The disk layout where the first PT sector describes several
partitions is incompatible with MS-DOS.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@xxxxxxxxxxxxxxxx
http://www.storagecraft.com

"Bill Schaible" <mr.correct@xxxxxxxxxxx> wrote in message
news:NdWdncxjguHfQ5_eRVn-ow@xxxxxxxxxxxxxx
> For years I've been using boot manager programs with multiple primary
> partitions on multiple drives. Or I skip the boot manager and use a disk
> editor to change the partition table in some cases. From that perspective I
> can't figure out what would be a proper definition for a 'primary'
> partition. I just spent hours Googling the subject on the internet and
> didn't find a real definition anywhere.
>
> Some facts about a primary partition (PP):
>
> (1) A PP is defined by one of the records in the partition table, as
> opposed to a logical volume, which doesn't have a record in the
> first physical sector (CHS001) of the drive. However, that's not a
> distinguishing feature because an extended partition has a record in CHS001
> also.
>
> (2) An extended partition begins with a partition table (in the EMBR), a PP
> does not. A true fact, but not a definition.
>
> (3) A PP doesn't necessarily need to contain system files. You can have
> the system files on a diskette, and only non-system files on the hard drive,
> and still have a workable system - i.e. a PP isn't necessarily bootable.
>
> (4) Maybe you could say it's a partition that's capable of being booted
> from if it has the correct system files and data structures. But that seems
> like an OS dependent definition. Is there a more rigorous definition
> somewhere?
>
> Bill S.
>
>
>
>


.

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